10-acyl derivatives of apoyohimbine and process therefor



United States Patent 3,120,529 ltl-ACYL DERIVATIVES 0F APDYQHIMBWE AND PRQCESS THEREFUR John Shavel, lax, Mendham, NJ assignor to Warner- Larnhert Firarrnaceutical Company, Morris Plains, N.J.,

a corporation of Delaware No Drawing. Filed Feb. 10, 1961, Ser. No. 88,307 4 Claims. {(Il. 260287) The present invention relates to new and novel -acyl derivatives of apoyohimbine of the formula:

CHsO wherein R is the acyl radical of an aliphatic carboxylic acid containing 1 to 6 carbon atoms and to the nontoxic acid addition and quaternary ammonium salts thereof. This invention also relates to a method of producing these compounds.

The compounds of this invention are derivatives of the alkaloid apoyohimbine of the yoh-imbane series. They have interesting pharmacological activity and are useful as analgesics, tranquilizers and hypotensive agents. In addition, they are valuable intermediates in the production of other compounds of the yohimbane series.

Included within the scope of this invention are such 10-acyl derivatives of apoyohimbine as IO-acetylapoyohmibine, 10-propionylapoyohimbine, lfl butyrylapoyohimbine, IO-valerylapoyohimbine and the like.

It has now been found that the compounds of my invention of the above formula may be prepared by treating the known apoyohimbine at between +25 C. and 40 C. with an acid anhydride or acyl halide having R acyl groups in the presence of a Friedel-Crafts catalyst. The reaction is one of acylation with an R acyl group being substituted at the l0-position of the apoyoh-imbine starting material. The reaction is carried out in the liquid phase under anhydrous conditions in the presence of a Friedel-Oraf-ts catalyst such as boron trifiuoride, aluminum chloride, aluminum bromide, stannic chloride, ferric chloride, ferric bromide, hydrofluoric acid, polyphosphoric acid, titanium tetrachloride, sulfuric acid and the like, with boron trifluoride being particularly eliective. The reaction mixture may also contain a carboxylic acid or a carboxylic acid ester corresponding to the acid halide or acid anhydride, that is, a carboxylic acid of the formula ROI-I, or an ester of the formula ROR wherein R is a lower alkyl group.

In carrying out the reaction the acylating agent (acid anhydride or acyl halide), either with or without the 3,12%,529 Patented Feb. 4, 1964 2 corresponding acid or ester, is initially saturated with catalyst at a temperature between about 20 C. and +10 C. The temperature of the mixture is then adjusted to the desired reaction temperature and the apoyoh-imbine starting material is added, either as a solid or as a solution in the acylating agent or in an inert organic solvent, such as methylene chloride, dioxan, tetrahydrofuran and the like. The reaction mixture is then stirred at the reaction temperature to completion and the product is recovered therefrom by conventional techniques of extraction, crystallization and chromatography.

'It is to be understood that the new and novel compounds of this invention may be used as the free base or may be converted into the corresponding pharmaceutically acceptable non-toxic acid addition and quaternary ammonium salts. Exemplary of non-toxic acid addition salts are those formed with male-lo, furnaric, ben- Zoic, ascorbic, succinic, bismethylensalicylic, methylsu-lfonic, ethanedisulfonic, acetic, propionic, tartaric, salicyclic, citric, gluconic, lactic, malic, mandelic, cinnamic, citraconic, ste-aric, palmitic, itaconic, iglyolic, benzenesulfonic, hydrochloric, hydrobromic, sulfuric, sulfamic, phosphonic and nitric acids. The acid addition salts may be prepared in the conventional manner, for example, by treating a solution or suspension of the (free base in an organic solvent with the desired acid, and then recovering the salt which forms by crystallization techniques. The quaternary salts are prepared by heating a suspension of the base in a suitable solvent with a reactive alkyl halide such as methyl iodide, ethyl bromide, n-hexyl bromide, benzyl chloride or a reactive ester such as methyl sulfate, ethyl sulfate or methyl p-toluene sulfonate.

For therapeutic use, the new and novel compounds of this invention, as the tfiree base, or as their acid addition or quaternary ammonium salts, may be formulated with conventional pharmaceutical carriers into dosage unit forms, such as tablets, capsules, elixirs, suppositories, solution, suspensions and the like.

The following example is included in order further to illustrate the present invention:

Example A mixture of 25 ml. glacial acetic acid and ml. acetic anhydride is saturated with boron trifiuoride at -10 C. by passing boron t-rifluoride into the solution for 15 minutes. The resulting mixture is cooled to --20 C. and 25 g. apoyohimbine are added. The reaction mixture is agitated for two hours and then is poured onto crushed ice. The suspension formed is made basic with ammonium hydrom'de and extracted with chloroterm. The extract is dried over sodium sulfate, filtered and evaporated to dryness. The residue, an oil, is crystallized from methanol to yield 19.9 g. of crystals, which on two further recrystallizations from methanol yield pure lO-acetylapoyohimbine (as the hydrate), lVLP. 20420'6 C. -(dec.), +38 (pyridine, c.=1.l).

Analys s.Calc.: C, 69.67; H, 7.12; N, 7.07. Found: C, 69.73; H, 7.43; N, 7.35.

It is understood that the foregoiing detailed description is given merely by way of illustration and that many variations may be made therein without departing them the spirit of my invention.

3 Having described my invention, what I desire to secure by Letters Patent is:

1. A member selected from the group consisting of compounds of the formula:

4 3. A method of preparing a compound of the formula:

R q N T H c=o CH3 wherein R is the acyl radical of an unsubstituted saturated aliphatic carboxylic acid of l to 6 carbon atoms which comprises treating apoyohimbine with a member selected from the group consisting of a carboxylic acid anhydride (R) O and a carboxylic acid halide R--X wherein X is halogen and R has the meaning above at a temperature between +25 C. and 40 C. in the presence of a Friedel-Crafts catalyst.

4. A method according to claim 3 wherein said Friedel- Crafts catalyst is boron trifluoride.

No references cited. 

1. A MEMBER SELECTED FROM THE GROUP CONSISTING OF COMPOUNDS OF THE FORMULA: 